1905] CURRENT LITERATURE 75 
Lanc'S has described in detail the single prothallus that he refers provision- 
ally to Psilotum; otherwise the gametophyte of Psilotaceae is entirely unknown. 
During his expedition to the Malayan peninsula, LANG found a number of plants 
of Psilotum growing on the stems of tree ferns, with rhizomes embedded among 
the adventitious roots covering the stems. In close association with one of these 
plants the single prothallus referred to was found. A preliminary account of its 
external form was published in rgor. It is thick cylindrical, about 6™™ long 
and 4.5™™ in diameter at the broad upper end. It shows the usual differentiation 
of the subterranean gametophytes of Lycopodium into vegetative region below 
and sexual region above. The latter appears as a thick overhanging margin in 
which numerous antheridia occur. The sexual region does not contain chloro- 
phyll, as in the Lycopodium cernuum type, the gametophyte evidently being 
entirely saprophytic. The vegetative region exhibits considerable aetucs 
differentiation, an endophytic fungus occupying a peripheral zone, and the central 
mass of tissue being entirely free from it. Some very interesting details in refer- 
ence to the fungus are given, especially the occurrence of some remarkable multi- 
nucleate “vesicles” borne upon it. If this gametophyte is that of Psilotum, the 
genus is closely related to the homosporous Lycopodiales; if it is not, it is certainly 
the gametophyte of some Lycopodium.—J. M. C. 
IN A RECENT number of Science MORGAN’? attempts an analysis of the phe- 
nomena of organic “‘polarity.”” He opposes the “formative stuff” hypothesis 
of Sacus and others, or rather that feature of it which calls for the migration 
of specific formative material, and arrays considerable evidence against it. 
MoreGan’s conception is that while the material which gives rise to new parts is 
totipotent, it is not homogeneous, so that it is different at different levels of the 
body, this difference being graded from one end of the organism to the other. 
This accounts for the gradation in the facility with which new parts are formed 
from one end to the other. Morgan also recognizes an organizing principle, 
which he calls the property of “‘formative organization,” ‘“‘which acts on the new 
and old parts as a whole and determines the relative arrangement and propor- 
tions of the new organs.” 
In regard to “‘polarity”’ in plants Morgan maintains that these same principles 
old. Assuming that there is a gradation from the distal to the proximal end of 
say, a mullen stem, in the size and vigor of the buds, the greater ability to produce 
shoots at the distal end is due merely to the fact that these buds are more vigor- 
ous and mature. The oe is made that the opposite may be true of the 
roots.—W. B. McCati 
18 LANG, WILLIAM H., On a prothallus provisionally referred to Psilotum. Ann. 
Botany 18:571-577. pl. 37. 1904. 
10 Morcan, T. H., An analysis of the phenomena of organic “‘polarity.””. Science 
20:712-748. 1904. 
